The present invention relates to the field of contactless controllers wherein the displacement of a carrier with respect to a reference frame is sensed without requiring an electrical contact between the carrier and reference frame. Controllers find application in such diverse areas as construction and agricultural vehicles, video games, computer graphics, robotics, and remote control. The controller serves as an interface between a human being and a computer or control system. The controller generates electrical signals in response to being manipulated by the user.
One convenient method of contactless sensing uses a magnet to establish a magnetic field and the displacement of the magnet with respect to a magnetically saturable core is sensed by the proportional part of the core which is saturated. Once saturation of a part of the core is achieved, any variation in the strength of the magnetic field is inconsequential. This principle has been applied to rotary and linear displacement sensors. A somewhat similar scheme senses the displacement of a magnet with respect to a semiconductor element exhibiting a magnetoresistive effect. The relative change in resistance of the semiconductor element is limited by the magnetic field strengths attainable with currently available magnets, however, and the response of the element is nonlinear and never achieves saturation. Thus, a magnetoresistive sensor is always responsive to variations in the magnetic field strength such as are caused by temperature variations, gap variations, and aging as well as changes due to displacement of the magnet. Kataoka et al. U.S. Pat. No. 3,691,502 issued Sept. 12, 1972, discloses that it is possible to obtain a device of this sort for detecting two-dimensional displacement by assembling two perpendicularly combined magnetoresistive devices. See FIGS. 33, 34. In FIG. 34, the magnetic field is of square shape having a central square space and takes a symetrical position over the magnetoresistive devices in the case of zero displacement. It is said that the voltages produced at center terminals independently measure the displacement in the orthogonal directions because the portions applied with magnetic field along one orthogonal direction are not changed by the displacement of the magnetic field in the other orthogonal direction. See Column 11, line 37 - Column 12, line 27. Kataoka et al. further described their magnetoresistive devices in U.S. Pat. No. 3,753,202 issued Aug. 14, 1973.
Another method of contactless sensing uses a differential transformer. Moller U.S. Pat. No. 3,331,972, for example, discloses a joy-stick controller which senses the angular tilt of a spherical member about each of two orthogonal axes. The spherical member includes a ferromagnetic core for a two-phase differential transformer. The spherical member also includes a recess into which a switch member yields when the spherical member is placed in its central position. The switch interrupts the current supplied to the excitation coils of the differential transformer, so that no displacement indicating signals are generated when the joy stick is in its central position.